[973000GTSL]

It's not that hard to build a basic box to fit in the back. First select which subs you want to use and find out the cubic air space required for the sub. Once you have that, building a box is easy. Lets say you are using a 10" woofer that requires .75cuft. lets say the only height spec is 12" tall or under. You use 1/2 mdf to build the box. So the OUTTER dim. are 12"X12"X8" the inside airspace would be 11"X11"X7" due to the 1/2mdf that would be 968cuin or .56cuft so you need to increase one dimension to increase the air space. Just run the inside dim. numbers till you are within the suggested space and add the thickness of the wood to the inner and you have your box. One think else to remember is that you can stuff the box to "trick" the sub that there is more airspace in a smaller box. Hope this helps. There are also programs you can get that will ask for the air space you want and a basic shape of the box and it will give you all your cuts to cut out the thinking.